Ready to Get Started?
Our doors & millwork specialists can help you find the right products for your project.
Browse › Doors & Millwork
Door Thresholds and Inserts
How to Pick the Right Profile, Material, and Seal
Doors & MillworkA threshold is the horizontal strip at the bottom of a doorway. It bridges the gap between the door bottom and the floor, providing a weathertight seal, a smooth transition between floor surfaces, and structural protection for high-traffic openings. That’s the job. Everything else — profile, material, insert type — is about matching that job to a specific opening.
For broader project planning, explore WBC’s doors and millwork resources.
For a Montana entry door facing -20°F outside and 70°F inside, the threshold decision is mostly about two things: thermal performance and seal material. Get those wrong and you’ll feel the draft every January. Get them right and the door does what it’s supposed to.
The good news on repairs: a worn seal usually doesn’t mean a new threshold. The vinyl insert that sits in the cap is the wear part, and it swaps out cheap.
Profiles: Match the Type to the Opening
Pick the profile first. It’s dictated by where the door is and what it has to do.
| Profile | Where it works |
|---|---|
| Saddle | General interior transitions; the workhorse for standard commercial exterior doors |
| Half-saddle / offset saddle | Uneven floor transitions where the two sides don’t sit level |
| Bumper / lip | Raised stop offering more weather protection — not ADA compliant |
| Interlock | Exterior doors needing the tightest weatherseal |
| Thermal-break | Insulated exterior doors that reduce heat transfer through the sill |
| ADA saddle / ramp | Accessible routes — 1/2-inch maximum height |
The saddle is the classic choice. The classic raised saddle threshold is the workhorse of standard commercial exterior doors. It creates a positive seal against weather infiltration and is available in aluminum, stainless steel, brass, and cast aluminum. When the floors don’t cooperate, half-saddle and offset saddle profiles accommodate uneven floor transitions.
For cold-climate exterior doors, the interlock is where it gets interesting. An interlocking threshold pairs with a matching door bottom sweep or door shoe to create the tightest possible weatherseal. The door bottom component hooks into or mates with the threshold profile when the door closes, blocking air, water, insects, and in some configurations, smoke. This system is well-suited to exterior entrances subject to weather extremes, and any opening where energy code compliance and thermal performance matter. Thermal break thresholds — which incorporate an insulating barrier inside the extrusion — go a step further by reducing heat transfer through the sill, supporting energy-efficient building envelopes.
That thermal-break/interlock combination is the right answer for a Montana exterior entry. The sill is exactly where water and cold want to get in, and the interlock plus thermal break shuts both down.
One caution on the bumper profile: it seals well but won’t pass an accessibility inspection. Saddle thresholds comply with ADA accessibility requirements. Lip or bumper thresholds offer greater protection from the elements but are not ADA compliant.
Material: Pick for the Environment
Material is the biggest durability variable. Here’s how the options map out.
| Material | Best use |
|---|---|
| Extruded aluminum | Most common commercial choice — lightweight, corrosion-resistant |
| Stainless steel | Corrosion resistance — food service, healthcare, harsh exposure |
| Cast aluminum | High-load and industrial openings |
| Brass / bronze | Decorative — historic, hospitality, institutional entries |
| Rubber / vinyl composite | Quiet interior transitions, ADA-friendly underfoot |
| Wood | Interior, where appearance matters |
Aluminum is the default for a reason. Extruded aluminum is the most common commercial choice — lightweight, corrosion-resistant, available in mill, dark bronze anodized, gold anodized, and black anodized finishes to coordinate with door and frame finish. On the engineering side, all aluminum extrusions are of alloy 6063-T5. When loads get heavy, step up: cast aluminum thresholds and heavy-duty extruded aluminum sill plates with abrasive inserts or non-slip grit surfaces are the right specification for forklift and cart traffic.
Now the part that matters most in this climate — the gasket material. Cold makes seals stiff, and stiff seals leak. The cold-flexibility ratings break down like this:
| Gasket material | Stays flexible to |
|---|---|
| Vinyl | -40°F |
| EPDM | -50°F |
| Silicone | -70°F |
Vinyl is an economical choice and remains flexible down to -40°F. EPDM gasketing is supplied both as a solid (dense) and as a closed cell sponge with a tough outer skin. It remains flexible down to -50°F. And at the top end, silicone gasketing provides the best resistance to cold by remaining flexible down to -70°F.
For a valley floor that sees deep cold snaps, vinyl covers most situations, but EPDM or silicone buy margin when the thermometer drops past -30°F.
On the composite threshold rail side, cellular PVC holds up to the weather swings. Cellular PVC rail is extremely resilient to long-term exposure to temperature changes, wind and snow loads, provides the appearance of natural wood but retains its color long term like a composite, and reduces maintenance with no staining or painting required. That’s a real advantage when freeze-thaw cycling chews up lesser materials.
Vinyl Replacement Inserts: The Cheap Fix Before Winter
Before anyone rips out a whole threshold, check the insert. The flexible vinyl strip riding in the cap is the wear part, and replacing it restores the seal without touching the aluminum base.
The replacement insert is made of durable vinyl and provides a seal to protect against drafts, moisture, dust and insects. The use of a soap and water solution is recommended to assist with installing this product. It’s a DIY job — easy to cut with scissors for trimming to desired length.
Inserts come in a range of profiles to match different thresholds:
| Profile (W x H x L) | Color |
|---|---|
| 1-1/2 in. x 3/4 in. x 36 in. | Gray |
| 1-1/2 in. x 3/4 in. x 72 in. | Gray |
| 2 in. x 5/8 in. x 36 in. | Gray |
| 1-1/4 in. x 3/4 in. x 36 in. | Gray |
| 1-1/4 in. x 3/8 in. x 36 in. | Gray |
| 3/8 in. x 5/16 in. x 36 in. | Gray |
| 1-25/32 in. x 5/8 in. x 36 in. | Brown |
Some inserts are made to fit specific adjustable-height thresholds. One 1-5/16 in. W x 1/2 in. D x 36 in. gray vinyl insert, for example, is specifically designed to fit adjustable height thresholds, particularly Model No. 08672. The lesson: match the insert profile to the cap groove it’s going into. They aren’t universal.
For thermal-break applications, there’s a rigid version. The Frost Insert is a gray rigid PVC front insert offering a 1/2-inch thermal break, with a maximum length up to 193-1/2 inches.
Western Building Center carries threshold and insert items including an oak threshold vinyl insert (36”), an economy threshold (36”), an under-door threshold (36”), and vinyl insert and door-sweep replacement options in the 36-inch range.
Measuring and Installation
Most field failures trace back to a bad measurement or a sill that wasn’t sealed and leveled. Get those two right and the rest is screws.
Measure width jamb to jamb, plus depth and height. Thresholds get ordered with a little extra to fit. All thresholds are to be ordered in 4-inch increments. Thresholds 48 inches and under are fabricated in standard sizes with 1/2-inch extra; thresholds over 48 inches are supplied with 1 inch extra length for fitting.
The install sequence:
- Check the opening first. Confirm the door swings freely and latches without binding. If the door drags or does not close properly, weatherstripping will not seal correctly.
- Level and clean the sill. Verify the floor surface at the door opening is level and clean. The threshold must sit flat against the floor to create a proper seal.
- Dry-fit and notch the ends to match the jamb profiles.
- Seal underneath. Lay continuous beads of exterior-grade sealant beneath the threshold and at the end dams — this is where water tries to sneak around.
- Fasten down. Pre-drill and screw. Most thresholds are furnished with mounting holes and #10 x 1-1/2 in. flat head sheet metal screws. Shims handle uneven floors.
- For adjustable types, raise the cap until it lightly contacts the door sweep — enough to seal, not enough to drag.
On press-on weatherstripping components, the timing matters: installation should take place after construction has been completed and final cleaning has taken place, the frame should be cleaned with isopropyl alcohol, and it’s not recommended for unsealed or porous applications.
ADA Height and Code
If the door is on an accessible route, the height and bevel aren’t negotiable. Commercial thresholds are specified to BHMA A156.21 standards.
Here’s what the rule actually requires:
- Maximum threshold height is 1/2 inch on accessible routes.
- Vertical change up to 1/4 inch is permitted without a bevel. Change from 1/4 inch to 1/2 inch must be beveled at a slope no steeper than 1:2.
- Change over 1/2 inch must be ramped at 1:12 — a threshold alone will not satisfy this; ramp construction is required.
- Existing and altered thresholds up to 3/4 inch are permitted if beveled on each side at 1:2 or less.
In practice, most new accessible entrances require a low-profile ADA ramp threshold or an accessible saddle profile, not a standard raised commercial saddle. Look for the right classification — ANSI J38103 and J37100 classified ADA ramp threshold options satisfy these requirements.
Frequently Asked Questions
Do I need to replace the whole threshold if it’s leaking air? Often no. The flexible vinyl insert in the cap is the wear part. The replacement insert goes in to replace an old and worn-out insert on an existing threshold; it’s made of durable vinyl and provides a seal to protect against drafts, moisture, dust and insects. It trims to length with scissors. Swap the insert before assuming the base is shot.
Which seal material holds up best in deep cold? It comes down to flexibility ratings. Vinyl stays flexible down to -40°F, EPDM down to -50°F, and silicone provides the best cold resistance at -70°F. Vinyl covers most situations; silicone or EPDM earn their keep when temperatures regularly run past -30°F.
What’s the difference between an interlock and a plain saddle? A saddle seats a sweep against a flat surface. An interlock mates mechanically. An interlocking threshold pairs with a matching door bottom sweep or door shoe; the door bottom component hooks into or mates with the threshold profile when the door closes, blocking air, water, insects, and in some configurations, smoke. For exterior doors in harsh weather, the interlock seals tighter.
How is a threshold sized and ordered? Measure width jamb to jamb, then depth and height. Thresholds are ordered in 4-inch increments. Units 48 inches and under come with 1/2 inch extra; over 48 inches come with 1 inch extra length for fitting. That extra is there so you can notch the ends to the jambs.
What fasteners hold a threshold down? Most thresholds are furnished with mounting holes and #10 x 1-1/2 in. flat head sheet metal screws. Pre-drill, set continuous sealant beneath, and shim where the floor isn’t flat.
Will a thermal-break threshold actually help my heating bill? That’s its whole purpose. Thermal break thresholds incorporate an insulating barrier inside the extrusion, reducing heat transfer through the sill and supporting energy-efficient building envelopes. The sill is a known weak point for heat loss, so cutting the conductive path through the aluminum matters where indoor-outdoor temperature differences are extreme.